The work proposed consists of a major project involving the amino acid sequencing of the serum glycoprotein, thyroxine-binding globulin. Other work proposed is an attempt to crystallize purified thyroxine-binding globulin. These two aspects are being carried out with a view to describing the chemical and conformational requirements for binding of the thyroid hormone, thyroxine, to its major serum transport protein. Additional work proposed is concerned with the binding of desialylated serum proteins, particularly thyroxine-binding globulin, to specific hepatocyte membrane receptors. In this regard, the effects of phenobarbital, a known stimulator of the smooth endoplasmic reticulum, will be studied by measuring the effect of this drug administered to rats on the ability of their hepatocyte membranes to bind desialylated glycoproteins. Also, the levels of circulating desialylated glycoproteins will be measured in treated rats before and after treatment.